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Research Article | Open Access

Synthesis of monolayer tungsten nitride: Rapid optical visualization and electrical impact of grain boundaries

Qiuyun Yang1,2,§, Dehu Li1,§, Fanfan Shi1,§, Zhibin Shao3, Na Wang2, Yao Peng1, Edwin Hang Tong Teo4, Zheng Liu4 (), Hong Wang1 ()
Department of Physics, University of Science and Technology of China, Hefei 230026, China
Institute of Electrical and Electronic Engineering, Anhui Science and Technology University, Fengyang 233100, China
College of Mechanics and Engineering Science, Hohai University, Nanjing 211100, China
School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore

§ Qiuyun Yang, Dehu Li, and Fanfan Shi contributed equally to this work.

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A chemical vapor deposition method was developed for synthesizing uniform monolayer tungsten nitride (W2N3) crystals on SiO2/Si substrates, and an effective wet-etch approach was introduced for the visualization of grain boundaries (GBs) using optical microscopy. Electrical measurements demonstrated that GBs of monolayer W2N3 hinder electrical conduction, serving as barriers to transport.

Abstract

Two-dimensional (2D) transition metal nitrides (TMNs) have garnered significant attention in fields such as energy storage and nanoelectronics due to their unique electrical properties, high chemical stability, and excellent mechanical strength. In polycrystalline 2D TMNs films, grain boundaries (GBs) are inevitable structural defects that could play a crucial role in determining the material's properties. Developing rapid optical visualization methods is essential for obtaining large-scale information on the distribution of GBs. However, the rapid visualization of GBs in 2D TMNs, as well as the impact of GBs on the material's electrical properties, has never been previously reported. In this study, we demonstrate the growth of monolayer tungsten nitride crystals on SiO2/Si substrates by chemical vapor deposition (CVD). High-resolution transmission electron microscopy reveals the presence of GBs at the junctions of twisted grains. A wet-etch process utilizing buffered oxide etchant (BOE) enables rapid and effective visualization of these GBs with optical microscopy. By analyzing grains with different twist angles, we find that GBs at specific angles demonstrate increased stability during etching. Electrical measurements revealed that tilted GBs hinder electrical transport, with GBs of a 62° twist angle showing sheet conductance nearly half that within the monolayer grain. This work not only provides insights into GBs in monolayer tungsten nitride but also lays the groundwork for exploring GBs-related properties in other 2D TMNs.

Keywords

two-dimensional (2D) materialsgrain boundarychemical vapor depositionelectrical propertytungsten nitride

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Nano Research
Volume 18 Issue 3,
March 2025
Article number: 94907242
DOI: 10.26599/NR.2025.94907242
Cite this article:
Yang Q, Li D, Shi F, et al. Synthesis of monolayer tungsten nitride: Rapid optical visualization and electrical impact of grain boundaries. Nano Research, 2025, 18(3): 94907242. https://doi.org/10.26599/NR.2025.94907242
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